1. Field of the Invention
This invention generally relates to cutlery, and, more specifically, to a folding knife that includes a locking spring that is integral with the blade.
2. Description of the Prior Art
Folding knives, especially of the pocket or hobby type, are generally provided with at least one locking mechanism for maintaining the blade in the open or fully extended position. Such locking mechanisms are used not only for facilitating the use of such knives but to enhance the safety in their use. Numerous mechanisms have been proposed to accomplish this objective. Two such mechanisms are illustrated in FIGS. 1-3.
A first mechanism is exemplified in FIGS. 1 and 2. In FIG. 1 a pocket knife is shown partially opened while FIG. 2 shows another knife of this type in the Fully open or extended position. Similar or identical parts are designated by the same reference numerals throughout. The knives are designated by the reference numerals 10, and include a handle 12 and an elongate folding blade 14 which is pivotally mounted on the handle 12 by means of a pivot pin 16. The blade 14 has a cutting edge 18 and an opposing edge 20 that meet at a point 22 at one end of the blade. An elongate groove or "common nail mark" is generally provided along the edge 24 which is normally accessible externally of the handle even when the blade is in the closed position and housed in a blade receiving space 12' of the handle 12 to thereby permit gripping of the blade with one's fingernail for opening the blade. The blade is pivoted at an end opposite to the pointed end which is commonly referred to as the "blade tang" 26. As will be noted, the blade tang is provided with a rounded end 28 and a cutout or "back square" 30 which defines a generally transverse stop surface or "run up" 32. Provided along one edge of the handle 12 is an elongate spring 34 having one end rigidly secured to the handle 12 by means of suitable fasteners such as rivets 36, 38. The other or free end 40 extends along the handle as shown and is provided with a generally transverse stop surface 40' which is dimensioned and oriented to mate with the surface 32 when the blade is in the fully open position as shown in FIG. 2. As is well known to those skilled in the art, the tang 28 is shaped in the form of a cam that applies a pressure to the spring end 40 when the blade is opened to urge the spring end outwardly, such pressure and movement typically peaking when the blade is approximately 90.degree. to the direction of the handle. The spring end 40, which acts as a cam follower, applies a counter force on the blade when it is placed under stress in this manner. The blade tang 26 is so shaped that the counter force applied by the spring tends to close the blade when it is partially closed, as suggested in FIG. 1, or tends to open the blade when it is mostly opened (i.e. when the blade extends an angle greater than 90.degree. with the handle.) When the handle is fully open as shown in FIG. 2 the spring end 40 is received within the cutout or notch 30 at which time the stress in the spring end 40 is fully eliminated. Any attempt to close the blade 14 from the position shown in FIG. 2 will be countered by the spring since this will again apply a stress to the spring. While the spring counter force can be overcome, and is overcome when the knife is to be closed, it is clear that the spring 34 serves as a locking device that inhibits free movement of the blade from the open position.
In FIG. 3, a similar knife 10' is shown, in which the spring 34 is replaced with two elements 34A and 34B. The element 34A, which may be although need not be resilient, is pivotally mounted on the handle 12' by means of pivot pin 38. The element 34B is a cantelever leaf spring having one end rigidly secured to the handle 12' by means of a spacer plate 42 which is itself secured to the handle by means of any suitable fasteners such as rivets 44. The other end of the spring 34B is arranged proximate to the rear portion of the element 34A (that portion between the pivot pin 38 and the spacer plate 42). As is well known to those skilled in the art, when the element 34A is in the position shown in FIG. 3, the spring 34B is unstressed. However, when the element 34A is rotated about the pivot pin 38 in a clockwise direction (as viewed in FIG. 3) the spring 34B is deflected and the stresses developed in the spring 34B urge the element 34A to remain in the position shown in FIG. 3. The front end of the element 34A (that portion to the left of the pivot pin 38 as viewed in FIG. 3) is provided with an inwardly directed rectangular projection 46 dimensioned and configurated to be received within a similarly shaped and configurated cutout 48 in the tang 26'. When the blade is in the open position the projection 46 prevents the free movement of the blade from the open position, the element 34A acting as a locking element. To close the blade the user must apply a pressure "P" as shown in FIG. 3 to overcome the counter force of the spring 34B, thereby rotating the element 34A sufficiently to remove the projection 46 from the cutout 48, thereby releasing the blade 14' and permitting same to be moved to the closed position. A folding knife employing such an arrangement is disclosed in U.S. Pat. No. 5,044,079.
Another locking device for a folding knife is disclosed in U.S. Pat. No. 5,293,690, in which a spring loaded crossbolt is fitted to the blade tang. One end of the crossbolt protrudes through an arcuate slot in the handle. A locking collar on the crossbolt engages locking counterbores located on the blade side of the opposite ends of the crossbolt slot. When finger pressure is applied to the end of the crossbolt, the locking collar is forced to disengage the locking counterbore and retreat to a relieved area on the blade. This permits the blade to be extended by forward finger pressure on the crossbolt. When the blade is fully extended, spring pressure forces the locking collar into the opposite locking counterbore, thus locking the blade. Reversing the sequence will close and lock the blade.
The disadvantages of the known constructions include the need for the handling and assembly of additional elements or components, including at least one spring, such as the spring 34 (FIGS. 1 and 2) or two or more springs or elements such as elements 34A and 34B (FIG. 34B.) Also, in addition to the extra cost of assembly, the use of additional parts represents an additional expense for a knife which has a relatively few number of elements. Therefore, the extra or separate springs or the like represent a significant percentage cost increase, particularly since the separate spring elements must be made of good quality spring steels. Additionally, when such extra elements are housed within the blade receiving space within the handle there is that much less room or flexibility within the handle to provide additional or auxiliary locking mechanisms for insuring that the blade will not inadvertently open when it is in the closed position.